This invention relates to an electroforming method and an apparatus for performing said method.
An electroformed article, for example, a nickel stamper is manufactured through the following steps:
First, a conductive matrix and an insoluble electrode having a high oxygen overvoltage are immersed in a nickel sulfamate bath. Voltage is applied between the matrix and electrode, to electrolyze the solution of nickel sulfamate, thereby depositing a nickel layer on the surface of the matrix. A nickel stamper is produced by peeling the nickel layer off the matrix. The above-mentioned matrix is formed of, for example, a glass plate coated with a thin silver electrode. The aforementioned insoluble electrode is prepared from, for example, a platinum electrode (disclosed in patent disclosure 61-3894, 1986).
During the electroforming process, azodisulfonate (hereinafter abbreviated as "ADS") is generated through the anodic oxidation reaction of sulfamate ion, in accordance with the following formula (1) (A.F. Greene; Plating, 55, 594 (1968)). EQU 2H.sub.2 NSO.sub.3.sup.- .fwdarw..sup.- SO.sub.3 -N=N-SO.sub.3.sup.- +4H.sup.+ +4e.sup.- ( 1)
After penetrating into an electroformed product, the above-mentioned ADS hardens and renders the product brittle. Moreover, once generated, ADS can not be decomposed by an oxidizing or reducing agent, or by heat treatment.
The drawbacks encountered until now, therefore, are that as integrated electric power is increased, the concentration of ADS in the electroforming solution is raised. Therefore, the more frequently the electroforming process is repeated, the harder and more brittle the resultant electroformed product. Finally, the problem arises in that the machining of the electroformed product is considerably difficult.